The broad goal of this research is to examine the normal course of the development of depth perception and motion processing in infancy. This proposal has two specific aims: First, to determine the relationship between the development of smooth pursuit eye movements and depth perception from motion parallax. Second, to compare the development of infants'sensitivity to depth from motion parallax and binocular stereopsis. Three experiments are proposed with two- to five-month-old infants. Stimuli for these experiments are designed to measure unambiguous depth, not shape or direction from motion as has been the case with some previous research. Moreover, multiple and converging measures are planned for a more convincing demonstration that infants perceive depth per se. The first two experiments involve an habituation/dishabituation paradigm, and include both a motion parallax and stereo version of the stimulus for comparison. Following habituation, recovery of looking time to a depth-reversed test stimulus will indicate discrimination, and thus good evidence for depth perception. Corneal reflective eye tracking data are expected to show a relationship between the development of smooth pursuit eye movements across the age range and depth from motion parallax. A third experiment uses the transfer-across-cues paradigm, where the infant is habituated to the stimulus specified by one depth cue, and then tested with the other depth cue. This research is an important step in determining the developmental relationship between motion perception, eye movements, depth from motion parallax, and binocular stereopsis. The development of motion parallax may serve as a foundation for stereopsis in higher cortical areas. Indeed, this hypothesis provides a parsimonious explanation for the dysfunctions found in eye movements, motion parallax, and stereopsis seen in the visual disorder esotropia. PUBLIC HEALTH RELEVANCE Infants perceive depth early in life from a variety of cues, including those that arise from the two eyes working together (binocular stereopsis) and from object and self- motion . This research may help to understand the development of certain visual disorders of motion and depth processing related to depth perception that are first evident in infancy.